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Advanced oxidation treatment of pulp and paper mill wastewater

page 621

62 ADVANCED OXIDATION TREATMENT OF PULP AND
PAPER MILL WASTEWATER
J. K. Murphy, Process Engineer
R. A. Hulsey, Process Engineer
Black & Veatch
Kansas City, Missouri 64114
R.K. Amarnath, Project Manager
Electric Power Research Institute
Palo Alto, California 94303
INTRODUCTION
Pulp and paper mills are facing more stringent limits on their discharges of process wastewaters. In
many cases, these limits are based on acceptable color levels, organics concentrations (both chlorinated and volatile), and biotoxicity. To meet the new limits, mill operators have changed their
bleaching processes in an attempt to reduce the use of chlorine, or have adopted an "end-of-the-pipe"
treatment approach. Depending on the plant layout, the type of wood being processed, and costs,
some mills may prefer to adopt the latter approach or a combination of the two approaches rather
than change their bleaching sequence. If this is the case, several treatment options are available to
attain compliance with the stricter regulatory limits. This paper discusses the results of a study
conducted to assess one such option.
To determine the feasibility of using ozonation and advanced oxidation processes (AOPs) to treat
process wastewater from an integrated pulp and paper mill, bench and pilot scale tests were conducted
on the process waste from a mill in South Carolina. Advanced oxidation processes combine ozone
with hydrogen peroxide or ultraviolet (UV) light to promote the formation of hydroxy radicals, which
are highly reactive. This testing program was undertaken by a consortium of pulp and paper mills,
power companies, manufacturers, and equipment suppliers under the direction of the Electric Power
Research Institute (EPRI). The goal of the program was to determine the technical and economic
feasibility of using AOPs to reduce color, organics concentrations, and the toxicity of several pulp and
paper mill wastewater streams.
New Color Limits
Among the water quality variables traditionally regulated in pulp and paper mill process wastewaters are BOD5 and TSS concentrations and pH. In recent years, some state regulatory agencies have
included limits on adsorbable organic halides (AOX) and, in some cases, effluent toxicity, in the
discharge permits of pulp and paper mills. In addition, numerical color limits have appeared in some
draft permits under regulatory review. Acceptable color levels are generally location-dependent and
are affected by the flow rate in the receiving stream and the volume of effluent discharged.
Discharge permits have always contained provisions for controlling color; however, the color limits
have generally been presented in such terms as "no objectionable color," which leaves enforcement to
the regulatory agency's discretion on a case-by-case basis. As water quality standards become stricter
and public pressure increases, regulators are rethinking their position on color limits. It is anticipated
that once one state begins to regulate color, many others will quickly follow.
In the past, treated effluents were quickly diluted in receiving waters, which minimized color
increase. Efficient in-stream diffusers have been developed which rapidly mix the treated effluent into
the receiving stream with minimal color change. In many cases, however, stream flow is not sufficient
to dilute the color, or the effluent is too highly colored. In these instances, compliance with numerical
color limits may become a challenge.
Some of the chemicals that cause or contribute to effluent color may be subject to water quality
standards, in which case the concentration of the individual chemical is limited by the NPDES permit.
48th Purdue Industrial Waste Conference Proceedings, 1993 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
621

62 ADVANCED OXIDATION TREATMENT OF PULP AND
PAPER MILL WASTEWATER
J. K. Murphy, Process Engineer
R. A. Hulsey, Process Engineer
Black & Veatch
Kansas City, Missouri 64114
R.K. Amarnath, Project Manager
Electric Power Research Institute
Palo Alto, California 94303
INTRODUCTION
Pulp and paper mills are facing more stringent limits on their discharges of process wastewaters. In
many cases, these limits are based on acceptable color levels, organics concentrations (both chlorinated and volatile), and biotoxicity. To meet the new limits, mill operators have changed their
bleaching processes in an attempt to reduce the use of chlorine, or have adopted an "end-of-the-pipe"
treatment approach. Depending on the plant layout, the type of wood being processed, and costs,
some mills may prefer to adopt the latter approach or a combination of the two approaches rather
than change their bleaching sequence. If this is the case, several treatment options are available to
attain compliance with the stricter regulatory limits. This paper discusses the results of a study
conducted to assess one such option.
To determine the feasibility of using ozonation and advanced oxidation processes (AOPs) to treat
process wastewater from an integrated pulp and paper mill, bench and pilot scale tests were conducted
on the process waste from a mill in South Carolina. Advanced oxidation processes combine ozone
with hydrogen peroxide or ultraviolet (UV) light to promote the formation of hydroxy radicals, which
are highly reactive. This testing program was undertaken by a consortium of pulp and paper mills,
power companies, manufacturers, and equipment suppliers under the direction of the Electric Power
Research Institute (EPRI). The goal of the program was to determine the technical and economic
feasibility of using AOPs to reduce color, organics concentrations, and the toxicity of several pulp and
paper mill wastewater streams.
New Color Limits
Among the water quality variables traditionally regulated in pulp and paper mill process wastewaters are BOD5 and TSS concentrations and pH. In recent years, some state regulatory agencies have
included limits on adsorbable organic halides (AOX) and, in some cases, effluent toxicity, in the
discharge permits of pulp and paper mills. In addition, numerical color limits have appeared in some
draft permits under regulatory review. Acceptable color levels are generally location-dependent and
are affected by the flow rate in the receiving stream and the volume of effluent discharged.
Discharge permits have always contained provisions for controlling color; however, the color limits
have generally been presented in such terms as "no objectionable color," which leaves enforcement to
the regulatory agency's discretion on a case-by-case basis. As water quality standards become stricter
and public pressure increases, regulators are rethinking their position on color limits. It is anticipated
that once one state begins to regulate color, many others will quickly follow.
In the past, treated effluents were quickly diluted in receiving waters, which minimized color
increase. Efficient in-stream diffusers have been developed which rapidly mix the treated effluent into
the receiving stream with minimal color change. In many cases, however, stream flow is not sufficient
to dilute the color, or the effluent is too highly colored. In these instances, compliance with numerical
color limits may become a challenge.
Some of the chemicals that cause or contribute to effluent color may be subject to water quality
standards, in which case the concentration of the individual chemical is limited by the NPDES permit.
48th Purdue Industrial Waste Conference Proceedings, 1993 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
621